A wideband wireless access system defines a terminal (MS), a base station (BS), and a router (ACR) to be compatible with an existing public IP network, and allows the terminal to have mobility, such that the terminal can use an IP-based network service during movement. An existing wideband wireless access system provides a structure in which one terminal enables communication with a base station through a frequency band that belongs to only one frequency assignment (FA).
Meanwhile, as an advanced type of the existing wideband wireless access system, an advanced wideband wireless access system has been suggested in which one terminal can communicate with a base station through a plurality of FAs. In this case, a function of allowing a terminal to communicate with a base station using a plurality of FAs is called a frequency overlay function. According to the advanced wideband wireless access system (hereinafter referred to as “frequency overlay communication system”), a connection structure between a base station and a public IP network is the same as that of the existing wideband wireless access system (hereinafter referred to as “non-frequency overlay communication system”), but a wireless access portion between the base station and the terminal is different from that of the non-frequency overlay communication system. That is, the base station and the terminal can communicate with each other through a plurality of frequency bands that are connected using two or more FAs. The frequency overlay communication system having the above-described structure has the following merits. If a wireless access method between a terminal and a base station and only a function of a MAC layer related to the wireless access method is slightly changed, it is possible to use a frequency band N times wider than that in the non-frequency overlay communication system (on the assumption that one terminal uses two FAs, a frequency band two times wider than that of the non-frequency overlay communication system can be used, and as a result, an available frequency band increases in proportion to the number of FAs used by the terminal). As a result, it is possible to increase a data transmission speed between the terminal and the base station by two times or more (generally, when the number of FAs used between the terminal and the base station is N, the transmission speed is increased N times faster than that of the non-frequency overlay communication system using one FA).
As this frequency overlay communication system is developed, a non-frequency overlay communication system and a frequency overlay communication system are mixed, which provides a mobile communication service to the terminal. As such, in a mobile communication system where a frequency overlay communication system and a non-frequency overlay communication system are mixed and a mobile communication service is provided, it is difficult to ensure that a terminal that is capable of performing a frequency overlay function (hereinafter referred to as “frequency overlay supporting terminal”) performs handover to a base station that is capable of performing a frequency overlay function (hereinafter referred to as “frequency overlay supporting base station”). Accordingly, when a frequency overlay supporting terminal that performs communication with a frequency overlay supporting base station using two or more FAs performs handover to a base station under the control of a non-frequency overlay communication system (hereinafter referred to as “frequency overlay non-supporting base station”), the frequency overlay supporting terminal can perform communication using a plurality of FAs. However, since the base station that is subjected to handover is a frequency overlay non-supporting base station, the base station can perform communication using only one FA. Therefore, there is a technical limitation in that the merits of the frequency overlay communication system are not sufficiently available.
Meanwhile, even when a frequency overlay supporting terminal performs handover from a frequency overlay supporting base station to another frequency overlay supporting base station, if a base station to which the frequency overlay supporting terminal performs handover does not know information indicating whether a plurality of FAs that can be used by the frequency overlay supporting terminal can use only adjacent frequency bands or both adjacent frequency bands and non-adjacent frequency bands, the following problem occurs. The frequency overlay supporting terminal can perform communication using only one FA depending on whether FAs allocated by the frequency overlay supporting base station are adjacent to each other.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.